1. Field of the Invention
This invention relates to a magnetic disk cartridge comprising a disk case, and a magnetic disk rotatably supported by liner members in the disk case.
2. Description of the Prior Art
In general, magnetic disk cartridges are constituted by securing a pair of disk-like liner members formed of a nonwoven fabric respectively to inner surfaces of upper and lower case halves of a disk case, and supporting a magnetic disk rotatably with respect to the disk case by the liner members. The liner members rotatably support the magnetic disk and clean the magnetic disk by catching dust, debris or the like clinging to the surface of the magnetic disk among fibers of the nonwoven fabric while the magnetic disk is being rotated.
In order to increase the cleaning effects of the aforesaid liner members, the liner members may be pushed strongly against the surface of the magnetic disk. However, when the liner members are strongly pushed against the surface of the magnetic disk, frictional resistance between the liner members and the magnetic disk increases, and it is not always possible to rotate the magnetic disk at a high speed. Particularly, in the case where the magnetic disk is used as a video floppy disk or a high-density recording disk, the amount of information which is to be transferred is large, and the magnetic disk must be rotated at a high speed for increasing the linear speed in order to increase the transfer rate of the information. However, the requirements cannot be satisfied when the frictional resistance between the liner members and the magnetic disk is high. Another approach to the improvement of the cleaning effects of the liner members is to increase the thickness of the liner members for improving the contact condition thereof with the surface of the magnetic disk, and not to increase the contact pressure so much. However, the liner members are formed of a nonwoven fabric, and unevenness of the thickness increases markedly when the nonwoven fabric is made thick. Therefore, such thick liner members are not suitable in practice.
One approach to elimination of the aforesaid problems is to form radial ribs on the inner surfaces of the case to which the liner members are secured, thereby to clean the surfaces of the magnetic disk by the liner member portions facin the ribs, and to decrease the areas of the liner members strongly contacting the surfaces of the magnetic disk, thereby to reduce the frictional resistance of the liner members with respect to the magnetic disk. However, in this case, the contact pressure differs markedly in the direction of rotation, i.e. in the circumferential direction, of the magnetic disk, and therefore the magnetic disk vibrates in the course of rotation thereof.